Most known chucking devices of this type are based on the principle that a radial pressure is exerted on the tool shank by the interaction of collet holder and collet, by means of which radial pressure the tool is securely held. In a frequently occurring form, the collet holder has an internal taper in which the equiangularly tapered collet is fixed by means of a chucking nut. The collet is slotted, so that it exerts a radial pressure on the inserted tool shank when being pressed into the collet holder (cf., e.g. WO98/32563).
In addition, an important aspect in the case of such chucking devices is the avoidance of unbalance. On the one hand, balancing means are usually provided, but, on the other hand, the possibilities of the occurrence of unbalance should be largely eliminated right from the beginning. This latter requirement leads to the stipulation that a chucking device should consist of as few individual parts as possible and should be geometrically designed as simply as possible. Thus, a chucking device which does not need a chucking nut is proposed in EP-668810. The collet or chucking sleeve is cylindrical and is held hydraulically in the receptacle. Therefore, although this embodiment has one part fewer, namely the chucking nut, the hydraulic arrangement is all the more complicated, so that this does not appear to be the optimum solution.
“Shrink-fit chucks” for thermally shrinking the tool shank in place constitute another solution approach. These certainly meet the requirement for the greatest degree of simplicity in design and the minimum of individual parts, but set against this are other disadvantages, such as, for example, the waiting times for cooling or the risk of burns during handling.
DE-4405242 discloses another form of chucking device which has an external taper on the collet and an internal taper on the receptacle and does not need a chucking nut. In this solution, the concentric-running properties are to be improved by the wall thickness of the receptacle being approximately constant in the axial direction due to a slight degree of taper. At the same time, a small wall thickness of the collet is proposed. Conflicting with this, however, is a very complicated construction of the device for drawing the collet into the taper socket.